The objectives of the present investigation are to determine whether prenatal or perinatal exposure to x-radiation (0.4-1.5 Gy) will result in behavioral and functional alterations in neonatal, young adult, and aged rats and to correlate such functional modifications with neuropathic changes. A preselected testing procedure will be utilized which incorporates conventionl teratologic studies, postnatal physiologic markers, neonatal reflex tests, and adult behavioral analyses in conjunction with selected histologic and biochemical analyses. Data acquisition will include a) fetal developmental parameters, b) perinatal and postnatal developmental parameters, and c) prenatal and postnatal functional and morphologic development of the central nervous system. The protocol consists of exposure of rats to 0, 0.4, 0.6, or 1.5 Gy on days 9 or 17 of gestation; 0, 0.15, or 0.30 Gy daily on days 15-19 of gestation or postnatal days 3-7; and 2.0 Gy on day 17 of gestation (this latter group will be used specifically to define the postnatal psychophysiologic characteristics of severe x-ray induced cerebral cortical hypoplasia). Teratologic evaluations will be completed on some animals at term, including complete dissection of all fetuses. The remaining rats will deliver their offspring. These offspring will be given five reflex tests and four physiologic parameter tests to be initiated on postnatal day 3. Randomly selected offspring of each litter will be raised without further testing until 700 days of age. The other offspring will be given a series of six adult behavioral tests which will begin on day 60. All offspring surviving to 700 days will be given the six adult behavioral tests. Selected young adult and aged offspring will also be tested under a stress paradigm and plasma norepinephrine, epinephrine, and corticosterone levels measured using a specially designed indwelling catheter. Several histopathologic techniques will be used to correlate functional changes with central nervous system morphologic alterations, including neocortical, allocortical, and cerebellar cortical morphology (axonal alterations, dendritic size, shape, and branching patterns, cell size, shape, location, density). These studies will extend our knowledge of the effects of prenatal and perinatal x-irradiation on postnatal psychophysiological development and function and their correlation with possible neuropathic alterations. These studies will assist in placing into prospective the relative sensitivity of neuro-physiologic, neuropathologic and anatomic effects of low level, in utero, radiation.